The storage of certain products such as granular sugar, grain and industrial fertilizers in bulk requires that the temperature of the storage space be maintained within a narrow range in order to avoid adverse effects on the stored product. In the case of sugar, for example, the atmosphere in contact with the sugar will have a humidity which is in equilibrium with the moisture content of the sugar. If the temperature varies, either throughout the entire storage space or locally within the space, moisture will migrate into or out of the sugar until a new equilibrium is established. In areas of increased moisture content, the sugar may become sticky whereas in areas of reduced moisture content the sugar may cake. Such effects are undesirable since they adversely affect the removal of the sugar from the storage unit by conventional bulk handling machinery.
For the bulk storage of sugar and other materials which are sensitive to temperature and/or humidity, it has been conventional to use large storage silos having provision for maintaining a uniform temperature within the storage space by heating or cooling the side, top and bottom walls of the structure. A typical storage silo, described in Weibull, U.S. Pat. No. 2,935,236, employed hollow side, top and bottom walls through which a stream of temperature conditioned air could be passed to maintain the interior of the silo at the desired temperature. In the Weibull structure, the outer insulation was spaced from the inner silo wall to provide a conduit for conditioned air. Because of the size of the structure, the outer insulation was installed in sections on a metal framework spaced from and supported by the inner silo wall. The inherent permeability of the insulating panels as well as the difficulty in sealing adjacent panels led to the loss of a substantial proportion of the conditioned air, thus increasing the cost of operating the structure. Other difficulties resulted from the necessity for handling and properly fitting many relatively large pieces of insulation, and erecting a scaffold for proper installation of the insulation. All of these factors increased the cost of constructing and operating such a system.